This invention relates to a mooring buoy for tanker ships, wherein the mooring operation takes place at the anchoring base of the buoy. Mooring buoys for tanker ships known, as "catenary mooring buoys" comprise a floating cylindrical body anchored to the sea bottom by means of a plurality of chains and to which the ship is moored, floating hoses, a rotary joint at the surface and one or more subsea hoses for connection to a subsea conduit. Buoys of the kind referred to above have the following defects:
frequent upkeep and replacement of the subsea flexible hoses, with a pollution hazard due to hose breakage;
hazard of serious damage to the buoy due to possible bumping of the ship, and
uneven stress at the points where the chains are anchored to the sea bed, with the ensuing necessity of oversizing the anchoring poles.
Another kind of mooring buoy for tanker ships, called an "articulated buoy" comprises a buoyant body anchored, via a cardan-type joint, to a baseplate placed on the sea bottom, and a rotary joint at the surface with a cardan-type joint at its bottom. A ship is moored relative to the portion of said body which emerges from the sea level, whereas the flow of the fluid to be loaded or discharged to and from the ship, from and to the submarine conduit, respectively, takes place via flexible hoses which are partly floating and partly immersed. This kind of buoy has the following shortcomings:
hoses which are partly immersed and which require frequent upkeep operations, like the buoy of the firstnamed type;
a bottom cardan-type joint which is both difficult and expensive to upkeep; and
the mooring of the ship at the sea level, which involves the pushing body which must have a considerable size.
Another kind of buoy is the one called a "single-chain buoy" and consists of a cylindrical floater which is anchored by a chain to a sea bed baseplate fastened by poles driven into the sea bottom. The hoses, partly floating and partly immersed, connect the ship to a rotary joint placed at the sea bottom.
The mooring cables of the ship are connected to the buoy body.
The defects are the same as those of the articulated buoy, since there is a rotary joint instead of a cardan-type joint at the sea bottom.